The present invention relates to an apparatus for mixing one or more powder and/or suspension materials with one or more liquid materials. The apparatus is particularly developed for the continuous manufacture of explosives by effective intermixing of the components thereof.
The apparatus according to the invention belongs to the static mixer category, i.e. a mixer in which the mixing occurs in a continuous flow without any moving parts other than the materials themselves.
Several types of static mixers are already known. In one known mixer a powder component is conveyed as a uniform stream in a conduit or on a plane surface while the other components to be included in the mixed product are sprayed into or onto the first stream, normal thereto, for example through spreading nozzles.
A second mixer is based on an ejector system in which one of the components may be the central jet and a second component is entrained by suction from a surrounding annular chamber.
In a third known mixer the components are initially conveyed together in a pipe, as a non-mixed, laminar and parallel flow discharging into an apparatus in which the flow is subjected to strong turbulence by repeatedly forcing and dividing it through a plurality of irregular plate channels.
For several mixing purposes the above mentioned known mixers suffer from certain deficiencies. The two first mentioned mixers will produce a non-homogenous mixture because the mixing zone will be located substantially at the surface layer of the main-stream. Furthermore, particularly with regard to the third mixer, there will be a tendency of plugging of the apparatus in such cases where the mixture gradually attains a sticky consistency.
A better solution to the problem of plugging or lump formation is provided by the disclosure of British patent specification No. 1,388,767 (based on a Japanish priority application No. 54935/71). According to this patent one powder component is gravity fed through a vertical pipe discharging down onto a power driven, rotating spreader cone that centrifugally disperses the powder into a liquid film flowing down the inner surface of a surrounding inverted truncated cone. The resulting compound is then further mixed on an underlying pin plate that rotates with the spreader cone.
However, also in this last mentioned apparatus there will be a tendency of lumping where the powder impinges on the liquid film supported on the walls of the inverted cone, and besides the relatively low velocities of the meeting component streams are not sufficient to secure an effective mixing of the materials, thus necessitating the above mentioned power driven post mixing. Thus, the apparatus according to the above British patent is not a static mixer and therefore, for safety considerations, is undesirable in the manufacture of explosives. Furthermore the apparatus is limited to the simultaneous mixing of not more than two materials.